After setting tiles on a surface, the joints between the tiles are filled with a joint filler. For decorative reasons, it is desirable to color the joints. Tinted cement-based tile grouts as joint filler have been gaining popularity because they provide unique and distinctive appearances.
Portland cement-based tile grout is a cost effective way to fill the spaces between tiles. Tile grouts are typically composed of Portland cement, sand, calcium carbonate and iron oxide and often, small amounts of spray-dried polymer and cellulose. The dry ingredients are blended, packaged and then mixed with water at the job site. The grout is installed and once cured, forms a hard, durable pigmented joint filler.
Portland cement-based tile grouts, however, have some disadvantages, particularly the lack of color consistency. Among reasons for the poor color consistency, efflorescence is a common issue with Portland cement, due to the lime that is produced during the cement hydration reaction and also common mineral impurities of sodium or potassium. Primary efflorescence typically occurs during the initial cure of the cement-based grout. Excess water is driven out as a result of the heat of hydration as the cement cures, bringing salts to the surface. As the water evaporates, it leaves the salt behind, forming a white deposit known as efflorescence. Secondary efflorescence can also form after the cement has cured, upon exposure to water.
Further, the degree of color inconsistency in a Portland cement-based tile grout can be affected by many factors. The amount of water used in the mix and the temperature and humidity conditions can affect the cement cure and contribute to increased efflorescence. The amount of water used in the grout clean up and the clean up procedure itself can also lead to increased efflorescence.